/*=========================================================================
 *
 *  Copyright Insight Software Consortium
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0.txt
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *=========================================================================*/
#ifndef itkGaussianBlurImageFunction_h
#define itkGaussianBlurImageFunction_h

#include "itkNeighborhoodOperatorImageFunction.h"
#include "itkGaussianOperator.h"
#include "itkGaussianSpatialFunction.h"

namespace itk
{
/**
 * \class GaussianBlurImageFunction
 * \brief Compute the convolution of a neighborhood operator with the image
 *        at a specific location in space, i.e. point, index or continuous
 *        index.
 * This class is templated over the input image type.
 * \sa NeighborhoodOperator
 * \sa ImageFunction
 * \ingroup ITKImageFunction
 *
 * \wiki
 * \wikiexample{Functions/GaussianBlurImageFunction,GaussianBlurImageFunction}
 * \wikiexample{Functions/GaussianBlurImageFunctionFilter,GaussianBlurImageFunctionFilter}
 * \endwiki
 */
template< typename TInputImage, typename TOutput = double >
class ITK_TEMPLATE_EXPORT GaussianBlurImageFunction:
  public ImageFunction< TInputImage, TOutput >
{
public:

  /**Standard "Self" typedef */
  typedef GaussianBlurImageFunction Self;

  /** Standard "Superclass" typedef */
  typedef ImageFunction< TInputImage, TOutput > Superclass;

  /** Smart pointer typedef support. */
  typedef SmartPointer< Self >       Pointer;
  typedef SmartPointer< const Self > ConstPointer;

  /** Method for creation through the object factory. */
  itkNewMacro(Self);

  /** Run-time type information (and related methods). */
  itkTypeMacro(GaussianBlurImageFunction, ImageFunction);

  /** InputImageType typedef support. */
  typedef TInputImage                              InputImageType;
  typedef typename InputImageType::PixelType       InputPixelType;
  typedef typename Superclass::IndexType           IndexType;
  typedef typename Superclass::ContinuousIndexType ContinuousIndexType;

  /** Dimension of the underlying image. */
  itkStaticConstMacro(ImageDimension, unsigned int, InputImageType::ImageDimension);

  typedef GaussianOperator<
    TOutput, itkGetStaticConstMacro(ImageDimension) >                            GaussianOperatorType;
  typedef Neighborhood< TOutput, itkGetStaticConstMacro(ImageDimension) >        NeighborhoodType;
  typedef FixedArray< NeighborhoodType, itkGetStaticConstMacro(ImageDimension) > OperatorArrayType;

  typedef GaussianSpatialFunction< TOutput, 1 >                        GaussianFunctionType;
  typedef typename GaussianFunctionType::Pointer                       GaussianFunctionPointer;
  typedef typename NumericTraits< InputPixelType >::RealType           InputPixelRealType;
  typedef itk::Image<
    InputPixelRealType, itkGetStaticConstMacro(ImageDimension) >       InternalImageType;
  typedef typename InternalImageType::Pointer                          InternalImagePointer;

  typedef NeighborhoodOperatorImageFunction< InputImageType, TOutput >    OperatorImageFunctionType;
  typedef typename OperatorImageFunctionType::Pointer                     OperatorImageFunctionPointer;

  typedef NeighborhoodOperatorImageFunction< InternalImageType, TOutput > OperatorInternalImageFunctionType;
  typedef typename OperatorInternalImageFunctionType::Pointer             OperatorInternalImageFunctionPointer;

  typedef itk::FixedArray< double, itkGetStaticConstMacro(ImageDimension) > ErrorArrayType;
  typedef itk::FixedArray< double, itkGetStaticConstMacro(ImageDimension) > ExtentArrayType;
  typedef itk::FixedArray< double, itkGetStaticConstMacro(ImageDimension) > SigmaArrayType;

  /** Point typedef support. */
  typedef typename Superclass::PointType PointType;

  /** Evalutate the  in the given dimension at specified point */
  virtual TOutput Evaluate(const PointType & point) const ITK_OVERRIDE;

  /** Evaluate the function at specified Index position */
  virtual TOutput EvaluateAtIndex(const IndexType & index) const ITK_OVERRIDE;

  /** Evaluate the function at specified ContinuousIndex position. */
  virtual TOutput EvaluateAtContinuousIndex(
    const ContinuousIndexType & index) const ITK_OVERRIDE;

  /** The standard deviation for the discrete Gaussian kernel.  Sets the
   * standard deviation independently for each dimension.
   * The default is 1.0 in each dimension.
   * If UseImageSpacing is true (default), the units are the physical units
   * of your image.  If UseImageSpacing is false then the units are pixels.
   */
  void SetSigma(const double *sigma);

  void SetSigma(const float *sigma);

  void SetSigma(const double sigma);

  itkSetMacro(Sigma, SigmaArrayType);
  itkGetConstReferenceMacro(Sigma, SigmaArrayType);

  /** Set the input image.
   * \warning this method caches BufferedRegion information.
   * If the BufferedRegion has changed, user must call
   * SetInputImage again to update cached values. */
  virtual void SetInputImage(const InputImageType *ptr) ITK_OVERRIDE;

  /** Set/Get the Extent of the array holding the coefficients
   *  of the Gaussian kernel computed by the GaussianOperator.
   */
  itkSetMacro(Extent, ExtentArrayType);
  itkGetConstReferenceMacro(Extent, ExtentArrayType);
  void SetExtent(const double *extent);

  void SetExtent(const double extent);

  /** Set/Get the maximum error acceptable for the approximation
   *  of the Gaussian kernel with the GaussianOperator.
   */
  itkSetMacro(MaximumError, ErrorArrayType);
  itkGetConstReferenceMacro(MaximumError, ErrorArrayType);

  /** Set/GetMaximumKernelWidth() This value is used by the underling
   *  GaussianOperator for computing the number of coefficients to be
   *  used in the Gaussian kernel
   */
  itkSetMacro(MaximumKernelWidth, int);
  itkGetConstMacro(MaximumKernelWidth, int);

  /** Set/GetUseImageSpacing() This flag is used by the underling
   *  GaussianOperator to decide if the image spacing should be used
   *  to scale the value of sigma or not. The methods UseImageSpacingOn()
   *  and UseImageSpacingOff() provide a similar functionality.
   */
  itkSetMacro(UseImageSpacing, bool);
  itkGetConstMacro(UseImageSpacing, bool);
  itkBooleanMacro(UseImageSpacing);

protected:
  GaussianBlurImageFunction();
  GaussianBlurImageFunction(const Self &);

  ~GaussianBlurImageFunction() ITK_OVERRIDE {}

  void operator=(const Self &);

  void PrintSelf(std::ostream & os, Indent indent) const ITK_OVERRIDE;

  void RecomputeGaussianKernel();

  void RecomputeContinuousGaussianKernel(const double *offset) const;

private:

  virtual TOutput EvaluateAtIndex(
    const IndexType & index, const OperatorArrayType & operatorArray) const;

  SigmaArrayType                        m_Sigma;
  OperatorImageFunctionPointer          m_OperatorImageFunction;
  OperatorInternalImageFunctionPointer  m_OperatorInternalImageFunction;
  mutable OperatorArrayType             m_OperatorArray;
  mutable OperatorArrayType             m_ContinuousOperatorArray;
  InternalImagePointer                  m_InternalImage;

  /** The maximum error of the gaussian blurring kernel in each dimensional
   * direction. For definition of maximum error, see GaussianOperator.
   * \sa GaussianOperator */
  ErrorArrayType  m_MaximumError;
  ExtentArrayType m_Extent;

  /** Maximum allowed kernel width for any dimension of the discrete Gaussian
      approximation */
  int m_MaximumKernelWidth;

  /** Number of dimensions to process. Default is all dimensions */
  unsigned int m_FilterDimensionality;

  /** Flag to indicate whether to use image spacing */
  bool m_UseImageSpacing;

  /** Neighborhood Image Function */
  GaussianFunctionPointer m_GaussianFunction;
};
} // end namespace itk

#ifndef ITK_MANUAL_INSTANTIATION
#include "itkGaussianBlurImageFunction.hxx"
#endif

#endif